I don't know if the 29er makes any difference but I would say go large! I had a medium racer x and am roughly the same size as you. As much as I loved the bike it was always just too small. So I've sold it and bought a large Scott Genius and will get a motolite Ti or El Guapo TI later in the year.

Large RX29

I'm 6-1 with a 36" cycling inseam, and I got a large. Actually, in more detail, I am 186cm tall, with a 152cm sternal notch, and a 91 cm cycling inseam. I can't give you a real strong recommendation on size, though, because I am still building this bike, but with a 90mm / 20 degree EA79 stem and a midrise EA70 bar and an EA70 seat post (with 10mm setback), the seat-tip to handlebar length is 22.5", which is perfect for me (based on my 26r set up, which I am really happy with). The one thing to consider, though, is that the large has an extra support tube from the top of the seat tube to the top tube (see photos below... red is Large and black is Medium). I guess this makes the Large heavier than a Medium, but probably a little more rugged. My Large is 6.8 pounds (frame with hanger and collar)... I hear the Mediums are 6.5 pounds. So that's what? ..... 135 grams heavier.... Doesn't matter to me. I am happy with my Large. But it seems like most people want a smaller frame with a longer stem. Not me. Just food for thought. I can't wait to finish this bad boy... XT drivetrain, brakes and wheels; Fox fork... wait a sec.... that's a different post. Happy trails.